Resistance alloy



Patented Oct. 11, 1927.

UNITED STATES 1,645,099 PATENT OFFICE.

TRUMAN S. FULLER, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

RESISTANCE ALLOY.

No Drawing.

The present invention relates to alloys and more particularly to alloys employed in connection with electrical apparatus and commonly known as resistance alloys.

In the construction of dynamo electric machines of the induction type, it is common to form the conducting bars and end rings of the rotor member from cast aluminum. Pure aluminum bars and rings, however, owing to their high degree of conductivity, are sometimes unsatisfactory for use in motors requiring a high starting torque, such, for example, as elevator motors and the like.

It is one of the objects of the present invention to provide a resistance alloy which has a higher resistance than aluminum but is suitable for use as conducting bars and end rings in induction motor rotors. Another object of the invention is to provide a resistance alloy capable of being cast in a manner similar to aluminum and not greatly exceeding' aluminum in cost of manufacture. A further object of the invention is to provide a resistance alloy which may be held molten in air for a considerable period of time without suffering any appreciable change in its composition or conductivity.

In carrying out my inventionI provide an alloy consisting mainly of aluminum but containing appreciable amounts of both manganese and zinc. Manganese and'zinc each have a tendency to reduce the conductivity of aluminum although zinc has alesser tendency to do so than the manganese.

. The use of zinc in the alloy, however, in

addition to reducing conductivity, provides analloy which is not so brittle as that which might be obtained by a combination of aluminum and manganese alone and which has other desirable features as well. For example, an alloy having a content of about 92% aluminum and 8% manganese has a resistivity equal to about 11.5 microhms per centimeter cubed. Such an alloy, however, may be foimd to be too brittle for certain uses. Addition of a small quantity of zinc to take the place of a portion of the manganese provides an alloy having the same degree of resistivity but a lesser degree of brittleness than the aluminum-manganese alloy. The addition of zinc to the aluminum-manganese alloy also performs another valuable func- Application filed February 25, 1927. Serial No. 171,075.

tion. The molten metal comprising the aluminum, manganese and zinc will usually have a temperature of about 825850 G. when castings are made from the alloy, and it is often necessary to maintain a given quantity of the metal in a molten condition in air while the rotors ofseveral machines are cast. It is desirable, therefore, that the composition and resistance of the alloy should not change materially during this period. I have found that by the addition of a small percentage of zinc to a molten alloy of aluminum and .manganese, the resultant alloy remains substantially unchanged in composition while maintained at a temperature of 825850 C. for prolonged periods of time and that there is no change in the resistivity of several rotors which may be cast from any one melt.

The zinc content of the alloy may range from about 2 to 8% of the total content of thealloy, and the manganese from about 4 to 10% 'of the content of the alloy, the remainder of the alloy being aluminum. I have found that if the alloy consists of approximately 90% aluminum, 6% manwill not greatly exceed the cost of pure.

aluminum, will have a resistivity equal to about 11.5 microhms per centimeter cubed, Y

and may be cast in a manner similar to aluminum. What I claim as new and desire to secure by Letters Patent. of the United States is 1. A resistance alloy consisting largely of aluminum and containing" appreciable amounts of manganese and zinc.

2. An alloy consisting largely of aluminum and containing from 4 to 10% of manganese and from '2 to 8% of zinc.

3. An alloy consisting of about aluminum, 6% manganese and 4%zinc.

4. A resistance alloy consisting largely of aluminum and containing at least 4% manganese and having a resistance equal to about. 11.5 'microhms per centimeter cubed.

5. A-resistance alloy consisting largely of aluminum and containing at least 1% of manganese and at least 2% of zinc.

In witness whereof, I have hereunto set my hand this 24th day of February, 1927.

' TRUMAN S. FULLER. 

